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Old 04-22-2017, 09:06 PM   #691
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Wanting to create a profile for my A800X my understanding is that the bulkheads are 0.5mm higher than the A800 and that it uses an AM06WL Hub which is 0.75mm higher than the A800 using AM06W. To account for that do I need to change the values for Y2 (+0.5 to 35mm) and LKing (+0.75 to 30.75mm)

When running the +0.5 width front balls for front arm sweep what do I need to change, my guess was X1 by 0.5mm?

Would appreciate your feedback, have a very dialled in A800 next to an A800X which I am about to throw at a wall! The changes to the car are probably great for carpet, high traction asphalt etc but for no traction, it sucks!
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Old 04-22-2017, 11:57 PM   #692
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Also the settings show a V Offset of -0.7 going from the AM06 to AM06M (which on the awesomatix info the AM06M is 13.58 vs 14.35 so around -0.7mm narrower but how do you account for the height difference, the AM06M is also shorter. I recall awesomatix saying to maintain the same roll centre you had to remove 2.5mm from the inner camber link. The A800 later ones had a AM06W Hub which was same height as the AM06 but 0.65mm wider again, and the A800X has a AM06WL hub which is the same width as the AM06W but 0.75mm higher.
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Old 04-26-2017, 07:34 AM   #693
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Quote:
Originally Posted by MikeXray View Post
Unfourtunately rubber tire TC's have proven flex to be an integral, and in some cases essential to a well performing car. If you look at many of the changes the top cars are making these days they revolve around flex. I can say that running 4 screws vs 6 in the rear part of the top deck of my T3 yeilds a different change than what can be achieved with a spring, link or droop change.
This whole idea has bothered me since day 1 of learning about rc racing. Millions, perhaps billions, of dollars is spent in the search for torsional rigidity, both on track and the street. I've asked high level rc drivers why do we purposely "add" or account for chassis flex? They don't know, like a lot of other things in rc they "just do it, it's how it's been forever". My opinion is its lazy. Something kind of works for someone so that's it, no discussion just follow everyone else, cuz that's how it is. Period. Bull, make the chassis stiff, and tune your suspension, why else have all this great suspension technology? Why not just make it a 1/10 pan car if you're going to negate a complicated and infinitely adjustable chassis system?! I feel similar regarding gluing the outer sidewall of tires to "cure" traction roll but that's another discussion. Just my 2 cents. Btw, thanks Bob for all your hard work, your program has been the funnest (most fun) thing I've purchased related to rc cars in a while.

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Old 04-26-2017, 08:19 AM   #694
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Chassis flex only seems to be desirable when grip is at a premium. Looking at real world race cars, F1 cars with tons of grip run super stiff chassis while a dirt oval car is intentionally much more flexible. When TC ran on foam, they had fairly stiff chassis but with rubber, softer seems to be better.

Of course, a lot of the reason for this has nothing to do with ultimate performance. In theory, a stiff chassis should always be better but in our RC world, it is virtually impossible to get everything exactly right. We just don't have the fine adjustability, hyper accurate set-up tools and proper shocks to get a setup spot on. Plus, very few RC racers have the knowledge and experience of a professional race engineer. We also don't have a butt in the seat to give precise feedback on what the car is really doing or telemetry to give us data. This is where flex comes in big. Flex disguises other set-up problems. A flexible car has a HUGE sweet spot it will work in set-up wise. It will also be less effected by changes in condition such as weather, grip level, tire type and condition, etc. So a flexible car will still work reasonably well with a sub-optimal set-up. It will NEVER work as well as a stiff car with a PERFECT set-up but with all the limitations I described, a perfect set-up is virtually impossible for us to ever attain.
A large amount of F1 suspension travel is in the sidewall of the tyres, if I recall it's a least 50%

Quote:
Originally Posted by roosterreagan View Post
This whole idea has bothered me since day 1 of learning about rc racing. Millions, perhaps billions, of dollars is spent in the search for torsional rigidity, both on track and the street. I've asked high level rc drivers why do we purposely "add" or account for chassis flex? They don't know, like a lot of other things in rc they "just do it, it's how it's been forever". My opinion is its lazy. Something kind of works for someone so that's it, no discussion just follow everyone else, cuz that's how it is. Period. Bull, make the chassis stiff, and tune your suspension, why else have all this great suspension technology? Why not just make it a 1/10 pan car if you're going to negate a complicated and infinitely adjustable chassis system?! I feel similar regarding gluing the outer sidewall of tires to "cure" traction roll but that's another discussion. Just my 2 cents. Btw, thanks Bob for all your hard work, your program has been the funnest thing I've purchased related to rc cars in a while.
'Normal' road cars have chassis flex built in as it improves the ride quality etc. For racing it's a different story.
I think part of the issue is that the laws of physics don't scale, they are the same whatever, and our tiny cars accelerate, corner and reach speeds (in comparison to scale) far greater than their full size equivalents.
It's the same when all slop etc is removed from suspension components in our cars, it makes them almost undrivable.
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Old 04-26-2017, 10:58 AM   #695
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Originally Posted by Skiddins View Post
A large amount of F1 suspension travel is in the sidewall of the tyres, if I recall it's a least 50%



'Normal' road cars have chassis flex built in as it improves the ride quality etc. For racing it's a different story.
I think part of the issue is that the laws of physics don't scale, they are the same whatever, and our tiny cars accelerate, corner and reach speeds (in comparison to scale) far greater than their full size equivalents.
It's the same when all slop etc is removed from suspension components in our cars, it makes them almost undrivable.
All cars factor in sidewall stiffness, in road cars it's cheaper to use a tire for optimal ride opposed to expensive suspension tech. In racing tire flex is more in the grip column (lateral vs vertical plane).
Physics do scale, macro OR micro, nano is stuff gets weird.
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Old 04-26-2017, 08:10 PM   #696
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does anyone have the sakura ultimate measurements?
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Old 04-27-2017, 02:30 AM   #697
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Quote:
Originally Posted by roosterreagan View Post
This whole idea has bothered me since day 1 of learning about rc racing. Millions, perhaps billions, of dollars is spent in the search for torsional rigidity, both on track and the street. I've asked high level rc drivers why do we purposely "add" or account for chassis flex? They don't know, like a lot of other things in rc they "just do it, it's how it's been forever". My opinion is its lazy. Something kind of works for someone so that's it, no discussion just follow everyone else, cuz that's how it is. Period. Bull, make the chassis stiff, and tune your suspension, why else have all this great suspension technology? Why not just make it a 1/10 pan car if you're going to negate a complicated and infinitely adjustable chassis system?!
I've seen similar posts on here before, but I'm yet to see a post from someone who has made a rigid chassis and gone any quicker

The cars haven't always been flexible. They started out rigid, following full-scale vehicle dynamics. Over the years they have evolved, as chassis flex gives more grip, better bump handling and a wider setup window.

Our cars are now about 500 times lighter than the lightest full-size race car. Yet they go at about one third the speed (mod TC >70mph). And they do it with much simpler suspension, tyres and aerodynamics. And they encounter curbs that come up to their axles, and bumps that would destroy a full-size car if scaled up.

When you put all that together, it's amazing the cars get round the track at all. So they need a lot of help, and flex is one of the things that helps. It keeps all 4 tyres in contact with the track, without resulting in any extra pitch or roll.

Give an old TC3 a go. The suspension geometry is similar to a modern car, but the chassis is ultra-stiff. See how it compares to a modern car.
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Old 04-27-2017, 03:22 AM   #698
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When you don't know why flex works it's easy to make assumptions and point fingers at suspension geometry. With flex you are making the car suspension closer to a live axle, or de Dion axle. They work good but everyone knows better ways. What we need is to apply the working principle behind flex/de Dion axle to an A arm suspension, instead of wildly guessing parameters.
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Old 04-27-2017, 05:17 PM   #699
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Quote:
Originally Posted by daleburr View Post
I've seen similar posts on here before, but I'm yet to see a post from someone who has made a rigid chassis and gone any quicker

The cars haven't always been flexible. They started out rigid, following full-scale vehicle dynamics. Over the years they have evolved, as chassis flex gives more grip, better bump handling and a wider setup window.

Our cars are now about 500 times lighter than the lightest full-size race car. Yet they go at about one third the speed (mod TC >70mph). And they do it with much simpler suspension, tyres and aerodynamics. And they encounter curbs that come up to their axles, and bumps that would destroy a full-size car if scaled up.

When you put all that together, it's amazing the cars get round the track at all. So they need a lot of help, and flex is one of the things that helps. It keeps all 4 tyres in contact with the track, without resulting in any extra pitch or roll.

Give an old TC3 a go. The suspension geometry is similar to a modern car, but the chassis is ultra-stiff. See how it compares to a modern car.
^ thank you for that, that's the first time I've personally seen someone actually explain it in a thoughtful way. It makes sense when put that way, we race to have fun and just so happens winning is very much more fun than losing, why not use every means at your disposal to make driving easier. I get that, I do. Just seems, to me at least, "flex" is an unknown quantity, whereas all the components meant to do that job are of known values and predictable...
But I guess if you've done the trial and error on adding or omitting certain chassis fasteners and figured out how it effects handling on the track what's the difference, it's a tuning aid like anything else I reckon.
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Old 04-27-2017, 05:29 PM   #700
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Originally Posted by roosterreagan View Post
^ thank you for that, that's the first time I've personally seen someone actually explain it in a thoughtful way. It makes sense when put that way, we race to have fun and just so happens winning is very much more fun than losing, why not use every means at your disposal to make driving easier. I get that, I do. Just seems, to me at least, "flex" is an unknown quantity, whereas all the components meant to do that job are of known values and predictable...
But I guess if you've done the trial and error on adding or omitting certain chassis fasteners and figured out how it effects handling on the track what's the difference, it's a tuning aid like anything else I reckon.
Id also like to point out that most if not all pro drivers are not engineers so they likely don't fully grasp how the physics work. They just Drive well and do it a lot, typically without knowing why something works, they just figure out that it does. I really like the explanation as well. An analogy that I like to share is comparing the scale of the racing surface. Both full sized cars and scale cars typically drive on the same surface... asphalt. What is considered smooth for a full sized car is a really rough cobblestone road to a 1/10th scale car. So consider going 600mph on a cobblestone road for a minute.
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Old 10-15-2017, 02:37 PM   #701
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Default home made dyno

Bob,
thought you may find this interesting.. Built it myself and will be importing data into RC3. Learned a lesson though with drag brake as my ESC blew while attempting to measure current. Was in awe that it was working, as I was seeing the data being plotted.

Thinking about the flywheel settings to use when importing, is there anything that I have to consider?


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Old 10-15-2017, 03:22 PM   #702
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Very nicely done. If you want power and torque numbers at the motor you will need to divide the chassis dyno flywheel inertia by the Overall Gear Ratio squared.

To get real anal the losses due to the dyno itself and the inertia of all the rotating bits of the car itself should also be included but that may be over the top. As long as you are not looking for absolute numbers at the motor that is not necessary. For doing relative comparisons you can ignore all that. You will need motor current and voltage data as well to import into RC3.

Looks like you are using an Arduino or Rasberry Pi for Data acquisition? I have done a similar thing with my MD2 Flywheel dyno. Big improvement over the MD2 Dyno.
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Old 10-15-2017, 07:45 PM   #703
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I am using an arduino, and also have current sensors, which are just behind the chassis, they are difficult to see. They are allegro, one is the 200amp version, and the second is the 50 amp to measure the current and voltage. The 200 amp is for mod motors and the 50 for stock.

What are you using to control the ESC, radio or software driven acceleration? Based on the photo it appears to be radio.

I am also building a 2nd flywheel version, will be similar to the mini pro, but without all the alluminum. What weight would you recommend for the flywheel?
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Old 10-15-2017, 08:19 PM   #704
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Perfect you should have no problem importing the data into RC3 then. What is the sample rate and spin up time with your rig?

I originally thought of doing a geared dyno like the miniPRO but now I think the direct drive method is better. Simpler and less losses to account for. I don't really like hanging the flywheel off the motor so I was going to support the flywheel on bearings. Motor to flywheel coupler will need to be a universal or something that can handle some misalignment. Just thoughts right now.

The mass of the flywheel will be a function of the gear ratio you plan to use and the desired spin up time. You can actually simulate a flywheel in RC3 with a little trickery.

If you run into any problems with the import let me know and I will do what I can to help.
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Old 10-15-2017, 09:45 PM   #705
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Sample rate right now is set at 9600 baud not sure of the spin up time, however the code used calculates RPM very fast from what I can tell. The RPM graph plots fairly nice, with a gradual exponential curve over a couple of seconds. I use a very small, yet strong neodymium magnet and hall effect sensor, and it reads with very little to no noise.

Thinking further to investigate why my ESC blew, I think the weight of the rollers may be too much. I built the rollers based on a comment I found from DamoRC himself where he said to double the weight of the car for each roller.
Using the simpledyno's setup calculator, I think each roller should be closer to 1320.5g, for a target roller mass of 2641g, giving an MOI of 0.003 kg.m^2

Currently each roller weight is approximately 4400g, which gives an MOI of 0.009 kg.m^2. Could this be too much and contributing to the failure of my ESC?

In one of your videos I see you have 24.06 mm^2 set for the flywheel inertia. Looking for your opinion
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